Barrier-to-autointegration factor (BAF) bridges DNA in a discrete, higher-order nucleoprotein complex

Barrier-to-autointegration factor (BAF) is a highly conserved cellular prot ein that was identified by its activity in protecting retroviral DNA agains t autointegration. We show that BAF has the property of bridging double-str anded DNA in a highly ordered nucleoprotein complex. Whereas BAF protein al one is a dimer in solution, upon binding DNA, BAF forms a dodecamer with DN A bound at multiple discrete sites in the complex. The interactions between BAF and DNA are entirely nonspecific with respect to DNA sequence. The dua l interaction of BAF with DNA and LAP2, a protein associated with the nucle ar lamina, suggests a role for LAP2 in chromosome organization. Consistent with this idea, RNA interference experiments with Caenorhabditis elegans re veal a defect in mitosis.